Nightguest
New Member
Hey there cool people,
If anyone has a moment, it would be awesome if I could get a sanity/safety check on my plans.
What I have right now:
Smart Solar RS 450/100
Multiplus 48/5000 (230v)
SOK 48/100
200A Class T Fuse on the battery
Cerbo GX managing this all
What I want to do is add a new 280Ah battery to this system, in parallel with the SOK, using a busbar to connect the batteries (with its own BMS).
However, before I make any connections, I want to check up on a few things since I've read a lot of contradictory things regarding paralleling batteries of different capacities.
Inverter Max Current Draw:
Inverter peak power: 9000W
Efficiency: Victron claims 96% max, however, my understanding is that this is at "ideal" so I'll use 90% efficiency.
Voltage: 51.2V
Max current draw (given the above): 195.3125A
(I got the max current by doing Power divided by efficiency divided by voltage.)
- First check, is that calculation right?
Sizing a BMS for 280Ah Battery
Is the current rating for a BMS
a/ Simply a measure of its max charge and discharge rate?
b/ An indicator for the maximum battery size it can handle?
If it is a/ then, would I be correct in understanding that if I were to use a 100A Seplos BMS, the only difference between this and using a larger amp BMS would be the charge/discharge?
I understand that there would be future issues that may arise, but, I'm much more likely to get a third battery before I get a larger inverter (I really want to get my hands on the upcoming EVE 560K LFP cells, but that's for another day!)
If it's not a/ could you please where I've gone wrong?
Parallel connection
So, this is where I get really lost.
What I want to do is connect the batteries in parallel via a good/proper bus bar, and have a dedicated fuse between each battery.
I've seen videos by Will and the Offgrid Garage where they mix multiple batteries of different sizes, however, I got told by the Seplos folks that I'd the second battery would 'have' to be the same capacity as the first one, this is without any communication between the SOK and the DIY one.
The communication part makes sense as the SOK uses a PaceBMS (if I remember right), and that's different, but the point about specific capacities "needing" to be the same threw me off a bit.
The question here is:
Is that true? Or is it just an "it's not recommended, but it will still work" thing? Or, is this just a Seplos issue?
Actually, extra question, since I'm going with a busbar + Fuse connection for the batteries, can I use "any" BMS, for example, one from JK, even if it doesn't specifically state that it supports parallel connections, or do I stick with BMSs that specifically say "supports parallel"?
Now about the fuse, here I've got a few questions:
1. Do I still size the fuse for the inverter, meaning that I'd need another 200A fuse between the battery and the battery bus bar, or, is that sized differently?
2. Is placing the fuse between the battery and the bus bar correct?
3. Would I need another fuse between the bus bar and my Lynx Distributor?
4. Originally, I was just going to keep things simple and cough up on another T-Class Fuse, however, I've seen some people write that using an MRBF fuse would be ok, however, they then also went on to say use a T-Class fuse. So the questions are:
- Would using a good-quality MRBF fuse instead of a T-Class fuse be ok?
- If so, where do I place them? Would they go on the battery terminals, or on the bus bar?
- In that case, would I still use a T-Class Fuse after the battery bus bar (between the battery bank and the inverter), or is that simply overkill?
Ok, that's all for now, sorry for the length of this, and thanks in advance to anyone that answers!
If anyone has a moment, it would be awesome if I could get a sanity/safety check on my plans.
What I have right now:
Smart Solar RS 450/100
Multiplus 48/5000 (230v)
SOK 48/100
200A Class T Fuse on the battery
Cerbo GX managing this all
What I want to do is add a new 280Ah battery to this system, in parallel with the SOK, using a busbar to connect the batteries (with its own BMS).
However, before I make any connections, I want to check up on a few things since I've read a lot of contradictory things regarding paralleling batteries of different capacities.
Inverter Max Current Draw:
Inverter peak power: 9000W
Efficiency: Victron claims 96% max, however, my understanding is that this is at "ideal" so I'll use 90% efficiency.
Voltage: 51.2V
Max current draw (given the above): 195.3125A
(I got the max current by doing Power divided by efficiency divided by voltage.)
- First check, is that calculation right?
Sizing a BMS for 280Ah Battery
Is the current rating for a BMS
a/ Simply a measure of its max charge and discharge rate?
b/ An indicator for the maximum battery size it can handle?
If it is a/ then, would I be correct in understanding that if I were to use a 100A Seplos BMS, the only difference between this and using a larger amp BMS would be the charge/discharge?
I understand that there would be future issues that may arise, but, I'm much more likely to get a third battery before I get a larger inverter (I really want to get my hands on the upcoming EVE 560K LFP cells, but that's for another day!)
If it's not a/ could you please where I've gone wrong?
Parallel connection
So, this is where I get really lost.
What I want to do is connect the batteries in parallel via a good/proper bus bar, and have a dedicated fuse between each battery.
I've seen videos by Will and the Offgrid Garage where they mix multiple batteries of different sizes, however, I got told by the Seplos folks that I'd the second battery would 'have' to be the same capacity as the first one, this is without any communication between the SOK and the DIY one.
The communication part makes sense as the SOK uses a PaceBMS (if I remember right), and that's different, but the point about specific capacities "needing" to be the same threw me off a bit.
The question here is:
Is that true? Or is it just an "it's not recommended, but it will still work" thing? Or, is this just a Seplos issue?
Actually, extra question, since I'm going with a busbar + Fuse connection for the batteries, can I use "any" BMS, for example, one from JK, even if it doesn't specifically state that it supports parallel connections, or do I stick with BMSs that specifically say "supports parallel"?
Now about the fuse, here I've got a few questions:
1. Do I still size the fuse for the inverter, meaning that I'd need another 200A fuse between the battery and the battery bus bar, or, is that sized differently?
2. Is placing the fuse between the battery and the bus bar correct?
3. Would I need another fuse between the bus bar and my Lynx Distributor?
4. Originally, I was just going to keep things simple and cough up on another T-Class Fuse, however, I've seen some people write that using an MRBF fuse would be ok, however, they then also went on to say use a T-Class fuse. So the questions are:
- Would using a good-quality MRBF fuse instead of a T-Class fuse be ok?
- If so, where do I place them? Would they go on the battery terminals, or on the bus bar?
- In that case, would I still use a T-Class Fuse after the battery bus bar (between the battery bank and the inverter), or is that simply overkill?
Ok, that's all for now, sorry for the length of this, and thanks in advance to anyone that answers!
